The present invention relates to a percutaneous or intratrocar surgical instrument for the excision and removal of a wide range of tissues. More particularly, a surgical cutting instrument is disclosed which is particularly adapted for a wide range of operating speeds, is flexible enough to navigate through tissue, and which is capable of cutting tough tissue such as may be found, for example, during orthopaedic or spinal surgery. The present invention has application in a wide range of procedures, although the following disclosure will pertain principally to minimally invasive cutting instruments used in the orthopaedic or spinal surgical fields.
In the field of spinal surgery, one problem that is frequently diagnosed and treated concerns degeneration or herniation of the intervertebral disk. In the past, treatment of these diagnosed conditions has required complicated and highly invasive surgical procedures often involving some degree of fusion between adjacent vertebrae serviced by the damaged intervertebral disk. In these procedures it is important that the infected disk be entirely removed for replacement by bone graft material. In some cases, a prosthetic disk may be implanted.
Within the last decade, techniques for percutaneous diskectomies have been developed. One such system is described in the patent to Onik, U.S. Reissue Pat. No. 33,258. The Onik device, like other known devices, is a "tube within a tube" cutting instrument which incorporates a reciprocating inner cutting sleeve operating within the central bore of an outer cutting sleeve. Typically, the excised disk material is suspended in a saline irrigation fluid which is aspirated through the central passageway of the inner cutting sleeve. A similar cutting device is represented in U.S. Pat. No. 5,106,364 to Hayafuji.
The tissue cutting instruments presently available in the art suffer from a variety of problems. Prior art linearly reciprocating devices are generally unable to cut very tough tissue, at least when an instrument sized for percutaneous insertion is used. Certainly larger cutting instruments driven by larger motors are capable of cutting very tough or hard tissue, but no prior device has been able to avoid the tradeoff between a minimally invasive cutting instrument and the capability to cut these types of tough tissue. As well, most prior art devices have blunt or rounded tips that undesirably push the very tissue to be cut out of the instrument's reach.
One significant deficiency of these prior devices is that many are not flexible to effectively navigate through rigorous tissue. Even worse, these old devices cannot be altered to make them flexible in their present configuration because the inside tubes bearing the reciprocating blade portions of these devices comprise one unit.
There is, therefore, a need in the field of tissue excision and removal for a surgical cutter that is adapted for minimally invasive uses, but that is still capable of reaching and cutting hard or tough tissue encountered in spinal and orthopaedic procedures, for example. A need also exists for a surgical cutter that has a tip configured to avoid trauma to tissues surrounding the tissue to be excised. A need exists for an instrument having a flexible drive feature that allows the reciprocating cutter to be bent to flex to reach the surgical site without sacrificing any cutting force. The cutting instrument must further be capable of excising the tissue cleanly, without tearing, and aspirating the tissue pieces effectively without clogging. These and other needs in the industry are addressed by the present invention.